The present application claims priority under 35 U.S.C. xc2xa7119 of German Patent Application No. 199 58 038.3, filed on Dec. 3, 1999, the disclosure of which is expressly incorporated by reference herein in its entirety.
1. Field of the Invention
The present invention relates to a process for increasing the water retention capacity in fibrous paper stocks in which a knead dispersing, which is known per se, is used in connection with further measures for achieving this goal.
2. Discussion of Background Information
It is known that the water retention capacity is an important feature of fibrous paper stocks and first influences the production conditions in the production of the paper in the paper machine. Additionally, it also influences the quality and usability of finished paper. Paper that was produced from a fibrous paper stock with a higher ability of retaining water has a better liquid intake capacity and an increased absorption capacity.
In the paper A Kriebel and R. Sigl, xe2x80x9cBeeinflussung von Fasereigenschaften durch Scheiben-Disperger und Knet-Dispergerxe2x80x9d in Wochenblatt fxc3xcr Papierfabrikation 23/24 1998, the effect of knead dispersers is described and explained in detail using various conditions and various original materials. Here, it is also mentioned that the increased porosity can be the result of a curling caused by knead dispersing. When performing the processes suggested here, obviously no improvement of the water retention capacity can be achieved; to the contrary, a lower deterring resistance is referred to as the result of this treatment.
Therefore, the present invention provides a process that improves the water retention capacity in fibrous paper stocks.
According to the process of the invention, a fibrous paper stock with a stock concentration of at least about 20% and a temperature greater than about 45xc2x0 C. is treated by knead dispersing for a treatment time of at least about 10 seconds, and, following the knead dispersing, a post-treatment phase to a machine tub of a paper machine is completed in a reaction time of no longer than about 30 minutes.
When combining a knead dispersing at relatively high temperatures and, consecutively, a rather short post-treatment phase, better water retention values can be achieved than have been available until now in the prior art. The desired effect can be achieved with the new process even while decreasing the grade of grinding or at least without increasing it.
Embodiments of the process according to the invention provide for an additional steam treatment of the paper fibers to occur, which can be performed, e.g., before or during the knead dispersing. The effect can also be supported by adding chemicals, e.g., ozone, which allows an additional improvement.
The present invention is directed to a process for increasing the water retaining ability of fibrous paper stocks. The process includes knead dispersing a fibrous paper stock having a stock concentration of at least about 20% and a temperature greater than about 45xc2x0 C. A treatment for the knead dispersing is at least about 10 seconds. The process further includes completing a post-treatment phase to a machine tub of a paper machine in a reaction time of no longer than about 30 minutes.
In accordance with a feature of the instant invention, the post-treatment phase can follow the knead dispersing.
According to another feature of the invention, the knead dispersing may be performed at a stock temperature greater than about 90xc2x0 C., further, the knead dispersing can be performed at a stock temperature greater than 110xc2x0 C.
A total specific work rate in the post treatment phase may not greater than about 10 kWh/to, and, preferably, the total specific work rate in the post treatment phase is not greater than about 5 kWh/to.
A temperature of the stock in the post treatment phase may be set at not greater than about 70xc2x0 C., and, preferably, the temperature of the stock in the post treatment phase is set at not greater than about 50xc2x0 C.
According to still another feature of the present invention, the reaction time of the stock in the post treatment phase may be a maximum of about 8 minutes.
Further, no machines for grinding paper fibers are utilized in the posttreatment phase.
In accordance with another feature of the invention, steam treatment of the paper stock may occur before or during the knead dispersing.
The process can further include introducing chemicals into the fibrous paper stock one of before and during the knead dispersing. The introduced chemicals may contain ozone gas.
Moreover,.the process may include increasing a temperature of the stock during the knead dispersing to a temperature of at least about 90xc2x0 C., and, preferably, the stock temperature during knead dispersing may be increased to at least about 110xc2x0 C. Further, the process can include reducing the temperature of the stock during the post-treatment phase to not greater than 70xc2x0 C., and, preferably, the stock temperature in the post-treatment phase may be reduced to not greater than 50xc2x0 C.
According to a further feature of the invention, the process can include introducing an amount of work to the stock during the post-treatment phase of less than about 10 kWh/to, and, preferably, the amount of work introduced to the stock during post-treatment can be less than about 5 kWh/to.
Moreover, the process may also include at least one of steam and chemicals to the stock one of before and during the knead dispersing. The chemicals can include ozone gas. Further, both the steam and the chemicals may be introduced to the stock one of before and during the knead dispersing.
The present invention is directed to a process for increasing the water retaining ability of fibrous paper stocks. The process includes knead dispersing a fibrous paper stock having a stock concentration of at least about 20% and a temperature greater than about 45xc2x0 C. A treatment for the knead dispersing is at least about 10 seconds. The process also includes post-treating the stock with a reaction time of no longer than about 30 minutes, and forwarding the stock to a tub of a paper making machine.
According to a feature of the present invention, the process can further include introducing chemicals into the fibrous paper stock one of before and during the knead dispersing. The introduced chemicals can contain ozone gas.
The process can also include further comprising increasing a temperature of the stock during the knead dispersing to a temperature of at least about 90xc2x0 C., and, preferably, the stock temperature during knead dispersing may be increased to at least about 110xc2x0 C. Further, the process may include, during the post treating, reducing the temperature of the stock to not greater than 70xc2x0 C., and, preferably, the stock temperature in the post treating may be reduced to not greater than 50xc2x0 C.
In accordance with another feature of the invention, the post treating may include introducing an amount of work to the stock during the post-treatment phase of less than about 10 kWh/to, and, preferably, the amount of work introduced to the stock during the post treating may be less than about 5 kWh/to.
In accordance with yet another feature of the instant invention, the process can further include introducing at least one of steam and chemicals to the stock one of before and during the knead dispersing. The chemicals may include ozone gas. Further, both the steam and the chemicals can be introduced to the stock one of during and before the knead dispersing.
Other exemplary embodiments and advantages of the present invention may be ascertained by reviewing the present disclosure and the accompanying drawing.